Self-contained power sypply and monitoring station for RF tissue ablation

ABSTRACT

A method and an apparatus is disclosed for delivering controlled heat to perform ablation to treat the benign prosthetic hypertrophy or hyperplasia (BPH). According to the method and the apparatus, the energy is transferred directly into the tissue mass which is to be treated in such a manner as to provide tissue ablation without damage to surrounding tissues. Automatic shut-off occurs when any one of a number of surrounding areas to include the urethra or surrounding mass or the adjacent organs exceed predetermined safe temperature limits. The constant application of the radio frequency energy over a maintained determined time provides a safe procedure which avoids electrosurgical and other invasive operations while providing fast relief to BPH with a short recovery time. The procedure may be accomplished in a doctor&#39;s office without the need for hospitalization or surgery.

RELATIONSHIP TO COPENDING APPLICATION

This is a division of application Ser. No. 08/368,936 filed Jan. 5,1995, now U.S. Pat. No. 5,540,655, which is a continuation ofapplication Ser. No. 08/061,072 filed May 14, 1993, now U.S. Pat. No.5,385,544, which is a continuation-in-part of application Ser. No.07/929,638 filed Aug. 12, 1992, now abandoned and a continuation-in-partof application Ser. No. 08/012,370 filed Feb. 2, 1993, now U.S. Pat. No.5,370,675.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is directed to a unique method and device for deliveringcontrolled heat to perform ablation to treat benign prosthetichypertrophy or hyperplasia (BPH). The method and the apparatus deliverthis controlled heat into tissue penetrated by devices such as thosedisclosed in the copending above-referenced applications.

2. Discussion of Background

Treatment of cellular tissues usually requires direct contact of targettissue with a medical instrument, usually by surgical proceduresexposing both the target and intervening tissue to substantial trauma.Often, precise placement of a treatment probe is difficult because ofthe location of a target tissue in the body or the proximity of thetarget tissue to easily damaged, critical body organs, nerves, or othercomponents.

Benign prostatic hypertrophy or hyperplasia (BPH), for example, is oneof the most common medical problems experienced by men over 50 yearsold. Urinary tract obstruction due to prostatic hyperplasia has beenrecognized since the earliest days of medicine. Hyperplastic enlargementof the prostate gland often leads to compression of the urethra,resulting in obstruction of the urinary tract and the subsequentdevelopment of symptoms including frequent urination, decrease inurinary flow, nocturia, pain, discomfort, and dribbling. The associationof BPH with aging has been shown to exceed 50% in men over 50 years ofage and increases in incidence to over 75% in men over 80 years of age.Symptoms of urinary obstruction occur most frequently between the agesof 65 and 70 when approximately 65% of men in this age group haveprostatic enlargement.

Currently there is no proven effective nonsurgical method of treatmentof BPH. In addition, the surgical procedures available are not totallysatisfactory. Currently patients suffering from the obstructive symptomsof this disease are provided with few options: continue to cope with thesymptoms (i.e., conservative management), submit to drug therapy atearly stages, or submit to surgical intervention. More than 30,000patients per year undergo surgery for removal of prostatic tissue in theUnited States. These represent less than five percent of men exhibitingclinical significant symptoms.

Those suffering from BPH are often elderly men, many with additionalhealth problems which increase the risk of surgical procedures. Surgicalprocedures for the removal of prostatic tissue are associated with anumber of hazards including anesthesia associated morbidity, hemorrhage,coagulopathies, pulmonary emboli and electrolyte imbalances. Theseprocedures performed currently can also lead to cardiac complications,bladder perforation, incontinence, infection, urethral or bladder neckstricture, retention of prostatic chips, retrograde ejaculation, andinfertility. Due to the extensive invasive nature of the currenttreatment options for obstructive uropathy, the majority of patientsdelay definitive treatment of their condition. This circumstance canlead to serious damage to structures secondary to the obstructive lesionin the prostate (bladder hypertrophy, hydronephrosis, dilation of thekidney pelves, etc.) which is not without significant consequences. Inaddition, a significant number of patients with symptoms sufficientlysevere to warrant surgical intervention are poor operative risks and arepoor candidates for prostatectomy. In addition, younger men sufferingfrom BPH who do not desire to risk complications such as infertility areoften forced to avoid surgical intervention. Thus the need, importanceand value of improved surgical and non-surgical methods for treating BPHis unquestionable.

High-frequency currents are used in electrocautery procedures forcutting human tissue especially when a bloodless incision is desired orwhen the operating site is not accessible with a normal scalpel butpresents an access for a thin instrument through natural body openingssuch as the esophagus, intestines or urethra. Examples include theremoval of prostatic adenomas, bladder tumors or intestinal polyps. Insuch cases, the high-frequency current is fed by a surgical probe intothe tissue to be cut. The resulting dissipated heat causes boiling andvaporization of the cell fluid at this point, whereupon the cell wallsrupture and the tissue is separated.

Destruction of cellular tissues in situ has been used in the treatmentof many diseases and medical conditions alone or as an adjunct tosurgical removal procedures. It is often less traumatic than surgicalprocedures and may be the only alternative where other procedures areunsafe. Ablative treatment devices have the advantage of using adestructive energy which is rapidly dissipated and reduced to anon-destructive level by conduction and convection forces of circulatingfluids and other natural body processes.

Microwave, radiofrequency, acoustical (ultrasound) and high energy(laser) devices, and tissue destructive substances have been used todestroy malignant, benign and other types of cells and tissues from awide variety of anatomic sites and organs. Tissues treated includeisolated carcinoma masses and, more specifically, organs such as theprostate, glandular and stromal nodules characteristic of benignprostate hyperplasia. These devices typically include a catheter orcannula which is used to carry a radiofrequency electrode or microwaveantenna through a duct to the zone of treatment and apply energydiffusely through the duct wall into the surrounding tissue in alldirections. Severe trauma is often sustained by the duct wall duringthis cellular destruction process, and some devices combine coolingsystems with microwave antennas to reduce trauma to the ductal wall. Fortreating the prostate with these devices, for example, heat energy isdelivered through the walls of the urethra into the surrounding prostatecells in an effort to kill the tissue constricting the urethra. Lightenergy, typically from a laser, is delivered to prostate tissue targetsites by "burning through" the wall of the urethra. Healthy cells of theduct wall and healthy tissue between the nodules and duct wall are alsoindiscriminately destroyed in the process and can cause unnecessary lossof some prostate function. Furthermore, the added cooling function ofsome microwave devices complicates the apparatus and requires that thedevice be sufficiently large to accommodate this cooling system.

Application of liquids to specific tissues for medical purposes islimited by the ability to obtain delivery without traumatizingintervening tissue and to effect a delivery limited to the specifictarget tissue. Localized chemotherapy, drug infusions, collageninjections, or injections of agents which are then activated by light,heat or chemicals would be greatly facilitated by a device which couldconveniently and precisely place a fluid supply catheter opening at thespecific target tissue.

SUMMARY OF THE INVENTION

It is a principal object of the present invention to provide a methodand an apparatus which delivers controlled heat to target tissue throughintervening tissues without substantially heating or effecting thoseintervening tissues. The target tissues are selected for medical actionsuch as tissue destruction. The destruction is limited to precisepreselected sites to minimize trauma and achieve a greater medicalbenefit.

One of the other principal objects of the invention is to provide amethod and an apparatus for precise tissue destruction of body tissuesby delivering therapeutic energy directly into the target tissue whileminimizing effects on its surrounding tissue.

Another object of the invention is to provide a method of thermaldestruction which is automatically controlled so as to shut off when asurrounding environment exceeds a predetermined temperature.

It is another object of the invention to provide a system for deliveringpower limited over a particular frequency range and limited over aparticular power range for a preselected period of time in order tocontrol temperatures in the adjacent tissues to the target tissue and inorder to provide parameters of power delivery so that the applied energydoes not affect body organs in the vicinity of the prostate and which donot affect any nervous system elements in the vicinity of said prostate.

It is a further object of the present invention to provide a timedapplication of RF power at a selected voltage and a selected frequencyrange to be delivered through a catheter. The type of catheter usedincludes a probe having a stylet guide housing with at least one styletport in a side wall and a guide means for directing a flexible styletoutward through a stylet port and through intervening tissues at apreselected angle into target tissue.

It is also an object of the present invention to provide a method and asystem which monitors the temperature in the environment of the probeend of the catheter by use of thermal sensors attached proximal to theflexible stylets and proximal to the stylet port wherein each of thesesensors provide a feedback indicating the display of the temperature.The invention also provides cut-off of RF power when the temperature ofany one of the sensors exceeds a respective predetermined maximum value.

It is also an object of the present invention to provide temperaturemeasurement in adjacent organs of the body of a patient with additionalsensors being used to monitor the effect of application of RF power onadjacent portions of the body.

It is a further object of the present invention to provide a voltagedelivery system and method which is based upon a calibrated delivery ofpower which calibration is based upon an impedance typical of a humanbody.

It is a further object of the present invention to provide for a methodof application of a controlled RF power for a predetermined period oftime having automatic switch off provisions based upon safetytemperature limits within the immediate environment of a catheterdelivering the RF voltage and within body organs adjacent to the area ofthe prostate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional drawing of the lower male anatomy showingthe placement of a catheter and a prostate probe with the catheterdelivering power according to the preferred embodiment of the method ofthe present invention;

FIG. 2 is a top view of a two stylet embodiment of an RF ablationcatheter utilizing the power application of the present invention;

FIG. 2A is a side-view of a non-conductive sleeve covering each styletof FIG. 2.

FIGS. 3a and 3b in combination show a schematic of the power supply forthe delivery system of the method of the present invention;

FIG. 4 is a view of the front panel of the power delivery system inaccordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The method of the present invention provides a precise controlleddelivery of RF energy to a tissue targeted for treatment or destruction.The generated power is delivered by means of a catheter providing astylet which includes a solid or hollow probe adapted to be passed froma catheter port through normal tissue to a target tissue. Typically thestylet is of the type disclosed in copending patent application Ser. No.07/929,638, abandoned and Ser. No. 08/012,370 U.S. Pat. No. 5,370,675. Astylet is shaped in order to facilitate easy passage through the issueand may be composed of a thin wire or rod or can be a thin hollow tubeor other shape having a longitudinal lumen for introducing fluids or forremoving materials. The stylet is usually and preferably formed withsharpened and reduced resistance when it is pushed through the tissue tothe target site. The stylet is designed, according to the presentinvention, as a radio frequency electrode.

The method of the present invention provides an improved medicaltreatment for destroying cells of medically targeted tissue throughoutthe body. These cells may be within or external to particular bodyorgans. Most particularly the method and the device for delivering theRF power useful for treating benign prostate hyperplasia (BPH) and thedevice and its use as described in the preferred embodiment are designedspecifically with respect to BPH. It will be readily apparent to aperson of skill in the art that the device and the method can be used todestroy body tissue and any other body cavity or tissue locations thatare accessible by percutaneous or endoscopic catheters and is notlimited to the prostate. Applications of the device and the method inall of these organs and tissues are intended to be included within thescope of this invention.

BPH is a condition which arises from the benign replication and growthof cells in the prostate, forming glandular and stromal nodules whichexpand the prostate and constrict the opening of the prosthetic urethra.Glandular modules are primarily concentrated within the transition zone,and stromal nodules within the periurethral region. Traditionaltreatments of this condition have included surgical removal of theentire prostate gland, digital removal of the adenoma, as well astransurethral resection of the urethral canal and prostate to removetissue and widen the passage way. One significant serious complicationassociated with the latter method is iatrogenic sterility. Morerecently, laser treatments have been applied to remove tissue, limitingbleeding and loss of body fluids. Balloons have also been expandedwithin the urethra to enlarge its diameter, with and without heat, buthave been found to have significant limitations.

Microwave therapy has been provided with some success by positioning amicrowave antenna within the prosthetic urethra and generating heat inthe tissues surrounding the urethra with a microwave field. Coolants aresometimes applied within the catheter shaft to reduce the temperature ofthe urethral wall. This necessitates complicated mechanisms to providecooling of the immediately adjacent tissues while at the same timegenerating heat in the more distant prosthetic tissue. This technique issimilar to microwave hyperthermia. Similarly, radio frequency tissuedestruction with electrodes positioned within the urethra has a limitedapplicability since it necessarily exposes the urethral wall todestructive temperatures. To avoid this, low temperature setting isrequired to protect the urethra and must be so low that the treatmenttime required to produce any useful effect is unduly extended, e.g., upto three hours of energy application.

In a preferred embodiment of the present invention, the urethra is usedto access the prostate and position RF stylets directly into the tissuesor nodules to be destroyed. The portion of the stylet conductorextending from the urethra to the target tissue is enclosed within alongitudinally adjustable sleeve which prevents exposure of the tissueadjacent to the sleeve to the RF current. Therefore, the ablativedestruction is confined to the tissue targeted for destruction, namelythose causing constriction. More particularly, according to the presentinvention the method of delivering power to the electrode stylets iscontrolled within a power range and frequency range and is limited by aseries of temperature sensors positions proximal to the stylets in orderto ensure complete protection of surrounding tissues. This is madepossible by an automatic cut-off of RF energy to the system upon thesensing of any one of the sensors exceeding a predetermined safetemperature for the region being treated. The method also featuresautomatic power cut-off using additional sensors placed proximal to bodyorgans adjacent to the tissue being treated in order to avoid damage tothose adjacent body organs due to increased organ temperature.

FIG. 1 is the schematic cross-sectional drawing of the lower maleanatomy during the use of a typical device for applying the controlledenergy to the treated tissue generated and delivered according to themethod and apparatus of the present invention. The urethra 2 extendsfrom the urinary bladder 4 through the prostate 6 and a urogenitaldiaphragm 8. BPH is a condition characterized by constriction of theportion of the prosthetic urethra caused primarily by proliferation ofbenign glandular and stroma cells in the prostate. These nodules pressthe wall of the urethra inwardly restricting the urethral diameter, andmay at times press normal tissue outwardly possibly enlarging theprostate. Traditional treatment, short of removal of the prostate, haveincluded either removal of tissue from the urethra to enlarge its lumenby resection or laser tissue destruction, or by expansion and heating ofthe tissues surrounding the urethra and to a temperature which causescell damage. The latter method is intended to reduce the swelling orenlargement of the prostate, and restore the urinary passage to at leasta portion of its former diameter.

A catheter 14 with a stylet guide 16 is passed downwardly through theurethra into the prostate. The position of the guide 16 is preciselycontrolled, using an ultrasound image, for example, obtained fromsignals received from the conventional ultrasonic transducer 18 insertedinto the rectum 20 adjacent to the prostate through the anal opening 22.The guide 16 facilitates easy positioning of the stylet 17 into aprecise location under ultrasonic imaging. The ultrasonic transducer 18may also contain sensors 37, 38 and 39 for sensing, within the bowelregion, any effects from heating tissue as will be described later.Optionally, the sensors 37, 38 and 39 can be a part of a separateinstrument placed into the rectal area after removal of an ultrasonicprobe and after the catheter 14 and stylet guide 16 have beenpositioned. The FIG. 1 illustrates two stylets 306 and 308 with thestylet 306 having its end penetrated into the tissue area 170 whichrepresents tissue to be ablated.

FIG. 2 is a top view of a two stylet embodiment of an ablation catheterof FIG. 1 used to deliver power from the preferred method and apparatusof the present invention. The flexible catheter 300, attached to handle302, has a terminal stylet guide 304 with two stylets 306 and 308. Thehandle has stylet sleeve cap 356 and electrode cap 354. The handle isalso connected to a RF power connector 303 to be discussed in detailhereinafter. Also shown is a connection for a thermoconnector 307. Theportions of the catheter 300 leading from the handle 302 to the styletguide 304 can optionally have a graduated stiffness. For example, thecatheter can be designed to be more stiff near the handle and moreflexible near the tip or any other stiffness profile desired. Thecatheter can be constructed of an inner slotted stainless steel tubewith an outer flexible sleeve such as is described in copendingapplication Ser. No. 790,648 filed Aug. 11, 1991, abandoned the entirecontents of which are incorporated herein by reference. It can also bemade of a coiled or braided wire to which an outer sleeve is bonded. Thestylet of FIG. 2 is described in the copending application Ser. No.08/012,370 filed Feb. 2, 1993, now U.S. Pat. No. 5,370,675.

The power delivery method of the present invention is enabled by thepower supply delivery system shown in the schematic of FIG. 3.

The block labelled 210 illustrates connections to the patient with theinserted stylet guide 16 and the transducer probe 18 having the sensors37, 38 and 39 in a manner similar to the FIG. 1. The stylet guide 16 hastwo stylets with the illustrated sensors 241 and 243 being respectivelyattached in the vicinity of the stylet. More particularly, in apreferred embodiment, the stylets 306, 308 of FIG. 2 each include anon-conductive sleeve as illustrated in FIG. 2A. This non-conductivesleeve is discussed in detailed in copending application Ser. No.08/012,370. For purposes of the present application, the non-conductivesleeve has a tapered leading tip 262 and a rigid proximal portion 264.The center portion or the inner lumen 274 of the non-conductive sleeve202 receives the stylet 306, 308. A temperature sensor 241 is mounted onthe tip. The mounting 243 shown schematically in FIG. 3 corresponds tothe other of the stylets and would be identical to the placement of thesensor 241. The third illustrated sensor in the stylet guide is labelled242 and corresponds to a placement inside the guide near the surface.The stylet guide is illustrated with the three sensors 241-243 whichsend temperature signals through the isolation device 231-233,respectively, in order to provide a temperature measurement at 221, 222,and 223, respectively.

The heating of the stylets 306 and 308 is accomplished through thegeneration of RF power by means of the crystal oscillator 102 and thetransformer circuitry 104 schematically shown in FIG. 3. The crystaloscillator in a preferred embodiment delivers effectively a 482 KHz RFpower to the stylet guide and more particularly to the stylets 306 and308, respectively. The transformer circuitry is calibrated for animpedance of 100 ohms. The impedance is based upon a median impedanceexpected in human patient measurements typical with placements ofstylets in the urethra. In the actual operation of the circuitry of FIG.3, the impedance varies from the calibrated impedance and this ismeasured by circuit 204. Because the delivery of the RF energy ismonopolar, each patient must have an indifferent electrode 206 tocomplete the circuit. Typically, these electrodes are large patcheswhich are placed on patient's back and are held by adhesive.

In a preferred arrangement, the transformer circuitry is capable of 16watts although the normal range of application for purposes of theisolated tissue ablation encountered in BPH is between 5 and 7 wattswhich is typically applied for three minutes.

The limits on the operation of the circuitry, aside from operatorsettings and frequency and power maximums, are determined by sensors241, 242 and 243 associated with the stylet guide 16 and sensors 37, 38and 39 associated with the rectal probe 16. The processing of theoutputs from the sensors 241, 242, 243 and 37, 38 and 39 are identicalas shown by the isolation devices 231 to 236 and the temperaturemeasurements 221-226, respectively. The isolation device 231-236involves a 1500 voltage isolation circuit which in a preferredembodiment is a Burr-Brown isolation device ISO 122JP. The output fromthis isolation device 231-236 is fed through cold junction compensators271-276 to the temperature measurement 221-226 circuits and totemperature cut-off circuits 211-216. Each of the isolation devices231-236 are identical as are the temperature measurement devices221-226. Each cold junction compensation structure 271-276 providesabsolute temperature measurement readings in degree Celsius. Althoughthe circuitry is the same for each of the temperature cut-off circuits211-216, each of these cut-off circuits have a different temperaturelimit or may have a different limit. Based upon physiological evaluationto insure against excess overheating in the environment of the tissuebeing destroyed and in adjacent organs, the following limits have beenset to provide protection to the patient. The sensor cut-off forcircuits 211 and 212 correspond to the sensors 241 and 243 and have asetting of 90° C. as a cut-off. To illustrate, a temperature of 60° C.is sufficient to provide for tissue protein dephasing which provides forthe destruction of the tissue. The temperature in the guide 16, asdetected by sensor 242 is set by the cut-off circuit 213 and atemperature of 45° C. This ensures that no damage occurs to the urethrain which the guide is placed. In other words, the material inside theurethra will not be destroyed if the temperature is maintained at 45° orless. It must be noted that if any one of the cut-off circuits operate,then the entire system is automatically shut-off regardless of anyoperator decisions. Thus, if either the sensors 241 or 243 reach 90° C.or if sensor 242 reaches 45° the device will shut off.

The purpose, as discussed previously, of the sensors 37, 38 and 39,which are typically located in a rectal probe 18, is to prevent adjacentorgan damage and particularly to protect against overheating of thebowel. This temperature setting in a preferred embodiment is set at 40°C. for each of the sensors 37, 38 and 39. Forty degrees C. is atemperature which is only slightly above normal body temperature (37.5°C.). Thus, once again, if any of the sensors 37, 38 and 39 exceed theirpredetermined cut-off limit, the entire operation of delivery of thepower to the stylets 306, 308 is shut down.

Also shown at FIG. 3 is a repetition rate adjuster 245 which can be usedto provide a pulsed output delivery of energy to allow for variation intime of delivery of energy based upon physiologic considerations. Thepulse output delivery of energy allows for electronic pulsing to providethe ability to adjust intervals between applications of energy in orderto provide bursts of energy which, when applied for a short time, doesnot cause any of the temperature sensors to exceed their predeterminedvalue but which delivers sufficient energy to kill cells in theimmediate vicinity of the stylet. After the application of such a spikeof energy, an interval before the next spike allows a total energyapplication to be of such a value as to not affect adjacent tissue areasor adjacent organs. In other words, the application of electronicpulsing provides an opportunity for applying an energy spike to have avery localized destructive effect in a short period of time while at thesame time restricting an overall total energy during a predeterminedperiod so as to not affect significantly affect adjacent tissue massesand body organs. The spike will be applied for a controlled short periodof time and have a controlled maximum level so that in an overall cycleof, for example three minutes, the total energy would either be the sameas or less than the energy applied during a continuous application whichenergy is calculated not to trigger any of the temperature sensorcut-off switches.

The electronic pulsing provides an opportunity, when necessary and whendesired, to more efficiently destroy cells in a very localized targetedarea and still maintain the safety of the method and the apparatus. Thetemperature limits of the sensor are not exceeded because, as indicatedabove, the total energy applied is not greater than that which would beapplied in a continuous operation.

The monitoring of the application of the electronic pulsing can beaccomplished manually based on observed temperatures on the monitor.That is, an operator could observe the approach of a temperature to thecut-off limit and stop the application of energy until a cooling offoccurs and then reapply the pulsing energy. Alternatively, suchmonitoring could be performed electronically based on preset parameterscontrolled by the necessary spiking of energy required to destroy acertain cell area and the subsequent electronic monitoring oftemperature increase and temperature decrease rates. None of theseelectronic pulsing steps either accomplished manually or electronicallybased upon physiological considerations would affect the safety thepatient because each of the temperature cut-off switches would stillfunction to automatically shut down the entire power supply if any oneof those temperature sensors either in adjacent mass tissue of thestylets or the sensor in the catheter guide in the urethra or anyadjacent body organ would exceed its preset safety temperature.Electronic pulsing either accomplished manually or through an electronicphysiological scheme provides an opportunity through the pulserepetition rate adjustor 245 to maximize the efficiency of thedestruction of the target mass tissue without adversely affecting thesurrounding tissue or adjacent body organs.

The operation of the power delivery system in accordance with the methodof the present invention will now be discussed in conjunction with FIGS.3 and 4 with FIG. 4 representing the front panel of a preferredembodiment of the operating system. The relationship between FIGS. 3 and4 is such that the outputs from the various measurements in FIG. 3labeled A-I refer to the displays A-I in the front panel of the powersupply of FIG. 4. Display A shows the power which is set by an operatorto be delivered by the supply and the transformer circuitry 104 inparticular. There is another power display B which is a display of theactual delivered power. As discussed previously, the power supply wascalibrated for an impedance load of 100 ohms. Any variance between theimpedance of 100 ohms and a particular patient will bring about slightvariations between the power which is set in the display A and thatwhich actually delivered and measured by circuitry 203 and displayed atB. In order to detect circuit completion, impedance measure 204 appliesa display of the impedance to the display panel C on the front of thedevice. The remaining displays D-I associated with the temperaturemeasuring devices 221-226 provide a display on the front panel of thetemperature of each of the sensors 241-243 from the stylet guide 16 andthe sensors 37-39 from the probe 18. Appropriate labeling on the frontpanel of FIG. 4 readily identifies which of the sensors is beingmonitored. It must be emphasized that the monitoring by the operator ofthe temperature is completely independent of the operation of thecut-off circuitry 211-216 which, as has been previously indicated,operates to automatically shut off the system regardless of any actiontaken by the operator. No further operation or restarting will occuruntil the temperatures of sensors decrease below their cut-off limitvalues.

In a preferred embodiment, connectors 47 and 48 provide for attachmentto the various probes with one of the connections 47 providing an outputto deliver power to the stylet as well as provide a sensor connection toreceive temperature signals from the three sensors 241, 242 and 243.Separate connector 48 receives the temperature delivered from sensors37, 38 and 39.

Although there have been illustrated three sensors associated with thestylet guide and three sensors associated with the rectal probe 18, itcan be readily seen that additional sensors or differently placedsensors may be used with temperature cut-off limits being set inrecognition of the physiological implications resulting fromtemperatures at other parts of the body.

Also in accordance with a preferred embodiment, the sensors 37-39 and241-243 are thermocouples although other forms of temperature sensorsmay be contemplated.

The RF energy frequency delivered by the preferred embodiment of theFIGS. 3 and 4 has, as mentioned previously, a frequency of 482 KHz.Other frequencies are available with the range being determined byfrequencies which do not substantially effect any physiological changewithin the body particularly as regard to the nervous system or anysensitive organs in the current path. Using those considerations, thefrequency range extends from above approximately 250 KHz in order toavoid damage based solely on the frequency of the signal. Other damageto be avoided of course results from the application of high voltagesand large power. Particularly, what must be avoided are large powersurges which can cause severe damage. Such large power surges canreadily occur in electrosurgery when a particular impedance is beingsignificantly altered as a result of tissue destruction. Such rapidchanges in impedance cause extremely high voltages to occur which canseverely damage adjacent nervous system elements and neighboring organfunctionings resulting in unacceptable rates of impotency.

The present method of power delivery avoids this drastic change inimpedance levels and particularly avoids surges of electricity basedupon the continuous delivery of constant energy with no significantvariation in the impedance of the circuitry.

In the alternate embodiment provided by the operation of the previouslydiscussed pulsing by repetition adjustment, the total energy over anysignificant period of time remains substantially constant and theimpedance level remains constant in sharp contrast to electrosurgerywhich has tremendously high energy peaks caused by breakdown inimpedance which often occurs during the electrosurgery operation withoutany reliable feedback control.

Tissue ablation in the desired area of treatment, in accordance with theembodiments of the present invention, results from the preciseapplication by way of the stylets of low power substantially constantenergy delivery resulting in minimal effect on the adjoining healthytissue and on neighboring nervous system elements and body organs.

For purposes of treating BPH the method of treatment using the powerdelivery system of the FIGS. 3 and 4 involves the operator applying anenergy level of between 5 and 7 watts for 3 minutes, followed byrepositioning of the stylet or stylets to other areas of treatment andthe subsequent reapplication for an additional 3 minutes of the samerange of energy. The number of applications is determined by the extentand the location of the tissue to be ablated. During each operation,temperature cut-off limitation circuitry affords the necessaryprotection due to any unexpected rise in temperature and the temperaturelimitations assure control of the environment immediately adjacent thetissues being treated as well as the urethra and any adjacent organs.The protection of the adjacent organs with respect to temperature riseis provided by the temperature cut-off limits associated with sensors37, 38 and 39.

Obviously, numerous additional variations and modifications of thepresent invention are possible in light of the above teachings. It istherefore to be understood that, within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed herein.

What is claimed as new and desired to be secured by Letters: Patent ofthe United States is:
 1. A self-contained power supply and monitoringstation for providing treatment in a human body by radio frequency of atarget tissue mass of a prostate of a human male having a bladder with abase and a penis with a urethra therein formed by a uretheral wallextending into the base of the bladder along a longitudinal axis andwith tissue of the prostate surrounding the urethra by use of a catheterinsertable into the urethra and having a stylet for entering the targettissue capable of penetrating the urethral wall and extending into thetarget tissue mass, the stylet including an insulating sleeve and atemperature sensor carried by the sleeve, comprising power supply meansfor delivering radio frequency energy continuously during treatment tosaid stylet at a frequency in a range which does not electronicallydamage human nervous system members but with an energy level which issufficient to ablate said target tissue, said power supply means furtherincluding circuitry adapted to be coupled to the temperature sensorcarried by the insulating sleeve, means for visually displaying thetemperature being measured by the temperature sensor, operator controlmeans for setting power delivered by said power supply to said stylet,and means for measuring power delivered to said stylet and temperaturecutoff circuitry adapted to be connected to the temperature sensor forautomatically shutting off the application of power to said stylet whena preset temperature is measured by said temperature sensor.
 2. Anapparatus according to claim 1, wherein said power supply means includesmeans for supplying an electronic pulsed energy output to said stylet.3. An apparatus according to claim 1, wherein said power supply meansprovides said radio frequency energy at a substantially constantpredetermined selectable value.
 4. An apparatus according to claim 2further including means for measuring impedance between the stylet andthe target tissue mass and the power supply for ascertaining when acircuit has been completed to the power supply.